The joint working group on the spectrum measurement of the Auger and TA collaborations estimated the relative difference in the energy determination of the two experiments at the level of \(6\%\)  (see [1]}, [2]} and references therein), that is perfectly compatible with the quoted systematic uncertainties of Auger \((14\%)\)  and TA \((21\%)\) . The UHECR fluxes measured by the two experiments are in a remarkable agreement up to energy around \(3\times 10^{19}\)  eV, see left panel of figure REF . Rescaling the Auger energies of \(+4.5\%\)  and the TA ones of \(-4.5 \%\) , well within the aforementioned uncertainties, the two observed fluxes show an excellent agreement apart from the highest energies, where the differences seem not conciliable (central panel of figure REF ). To understand if this discrepancy has a physical origin related to the different sky portions observed by the two experiments, in the right panel of figure REF  we have plotted the spectra observed using only UHECR events arriving in the common declination band of Auger and TA (\(-15^\circ \le \delta \le 24.8^\circ \) ). Restricting the analysis to this sky portion the agreement improves, but at energies larger than \(3\times 10^{19}\)  eV the differences remain sizeable and cannot be explained by an independent scaling of the energy reconstruction in the two datasets. It should also be remarked that the energy spectrum measured by Auger does not show any dependence on the declination, while that observed by TA does, with some tension related to the expected UHECR anisotropy [1]}, [2]}. Given the uncertainties in the energy determination and the poor statistics, it is too early to draw any definite conclusion on the reason of the differences between Auger and TA in the spectrum measurement at the highest energies.
